A device disclosed in Japanese Patent Application Publication No. 2011-67093 (JP 2011-67093 A) (Patent Document 1) is known as such a drive device as described above. The device of Patent Document 1 includes rotary electric machines (motor-generators 192 and 194 and a motor for accessories 195) and inverters (inverter devices 140 and 142 and an inverter device for accessories 43) controlling the rotary electric machines. The inverters are accommodated in dedicated inverter cases (an upper case 10, a housing 12, and a lower case 16). The inverter cases are fixed to a drive device case accommodating the rotary electric machines. As a result, such dedicated inverter cases need to be prepared, so that the number of components increases, and the overall size of the device also increases.
To control drive of the rotary electric machine (the motor-generators 192 and 194 and the motor for accessories 195), a current sensor for detecting a current flowing in a stator coil of each phase should be provided. The conventional current sensor used in the drive device generally uses a Hall element. The sensor using the Hall element has relatively stable temperature characteristics and can accurately detect the current, and hence, is often used to enable accurate drive control of the rotary electric machine in the drive device, which tends to be subjected to a high temperature environment. The sensor using the Hall element is, however, generally expensive, thereby contributing to an increase in cost.
With respect to this point, in the case of for example, electrical appliances, such as an air conditioner, techniques are known in which a shunt resistor provided in an inverter circuit is used to detect the current flowing in the stator coil of each phase of the rotary electric machine (Patent Documents 2 to 4). The shunt resistor is inexpensive, and hence, the product cost can be lower than that in the case of structuring the rotary electric machine such that the current is detected by the sensor using the Hall element. However, no example applying such a shunt resistor to current detection for a rotary electric machine in a drive device has been known.